The subdivision regulations adopted by the counties of Giles, Clarke, Culpeper, Loudoun or Mecklenburg shall apply in all the unincorporated territory of the county; provided, that no such regulations to be effective in the area of the county subject to municipal jurisdiction shall be finally adopted by the county until the governing body of the municipality shall have been notified in writing of such proposed regulations, and requested to review and approve or disapprove the same, and if such municipality fails to notify the governing body of the county of its disapproval of such regulations within forty-five days after the giving of such notice, the same shall be considered approved; and provided further, that if the municipality has a duly appointed planning commission, the governing body of the county or its agent shall give such notice to such commission as is required to be given the county planning commission by § 15.2-2248, and the provisions of that section shall apply, mutatis mutandis, to the actions of such commission and the governing bodies of the county and city, respectively.